测试表明, 690TT合金划痕周围形成了加工硬化区, 范围可达100 μm. TEM及EBSD-OIM组织观察发现, 划痕沟槽处的基体组织出现了一定程度的纳米化. 在330 ℃碱溶液中的浸泡实验表明, 划伤诱发了690TT合金应力腐蚀裂纹的萌生和扩展, 划伤过程中形成的变形晶界、孪晶界以及产生的微观裂纹成为应力腐蚀裂纹优先萌生的位置. Pb的存在使氧化膜变得疏松, 加速了基体的溶解和氧化. 随着溶液中Pb含量的增加, 划伤诱发的应力腐蚀裂纹长度随之增加. 690TT合金表面划伤严重降低了材料抵抗应力腐蚀开裂的能力.
The microstructure and stress corrosion cracking (SCC) behavior of scratched zone on alloy 690TT were studied by using microhardness, TEM, EBSD-OIM and immersion experiment in caustic solution. It was found that a deformed hardening layer with a dimension range of 100 $\mu$m was produced near the scratch. TEM and EBSD-OIM observations showed that the grains at shallow surface of scratch groove were refined to nano-size. SCC tests for scratched alloy 690TT were performed in caustic solution at high temperature with or without addition of lead oxides. The results showed that SCC cracks initiated and propagated at scratch banks and scratch grooves. Grain boundaries, twin boundaries deformed and microcracks produced during scratching process are preferential sites for SCC. The oxide films formed on scratch groove were loosed by lead. The SCC crack length increased with increase of lead content. Scratched alloy 690TT is susceptible to SCC.
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